In the Duck Detective Plane,
"Ah, Aunt, isn't this that time we went to London, England?" Weller remembered that he and his Aunt teamed up to crack a major espionage case back then. Of course, as to how they cracked it, you must forgive him for not being able to tell anyone else.
Because at the time, it was simply because he told his Aunt the classified details of the relevant case that he ended up being cursed out from head to toe by the bald Chief Inspector who happened to arrive at the police station, and he was even fired afterward.
Chapter 603